Electrical telecommunication systems



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W- R Y United States Patent 9 ELECTRICAL TELECOMMUNICA'I'IGN SYSTEMS John Scowcroft, Coventry, England, assignor to The General Electric Company Limited, London, England Application March 4, 1955, Serial No. 492,063

13 Claims. (Cl. 179-18) This invention relates to electrical telecommunication systems in which trains of electrical impulses are employed to set switches so as to establish a signalling path between a calling station and a called station, the said impulse trains being initiated under the control of the calling station, as for example by means of a telephone dial. The invention is more particularly concerned with such systems in which provision is made so that when the calling station and the called station are associated each with a different switching centre, such as an automatic telephone exchange, some of the impulse trains are translated into further impulse trains which are employed to establish a signalling path between the originating switching centre of the calling station and the objective switching centre of the called station, either directly or by Way of one or more intermediate switching centres, and other of the impulse trains are employed at the objective switching centre to extend the signalling path to the called station.

in automatic telephone systems of this kind it is known for a calling party to dial a series of say seven digits of which the first three, the so called routing digits, characterise the objective telephone exchange, and the remaining four digits represent the directory number of the wanted party at that exchange. The trains of impulses corresponding each to a different one of the dialled digits are received by the exchange, hereinafter referred to as the originating exchange, to which the calling Sl3.-"

tion is connected, by line wires, where the first three impulse trains are usually translated into further trains of electrical impulses, the so called route code. The impulse trains of the route code are employed to extend a signalling path from the originating exchange to the objective exchange over a predetermined route, this route usually being by way of one or more intermediate telephone exchanges. The last four impulse trains are transmitted unchanged to the objective exchange where they are employed to set switches so as to select the telephone station of the wanted party. As the interval between successive impulse trains of such a series is small it is usual to store at least the last four impulse trains in a register until the route of the objective exchange has been established.

It is an object of the present invention to provide an improved arrangement whereby translation may be effected of trains of electrical impulses, such translation being with or without change in the number of impulses in an impulse train and with or without change in the number of trains.

According to the present invention, an arrangement for use at a switching centre of a telecommunication systemof the kind in which trains of electrical impulses are employed to effect switch setting and which is adapted to translate information in the form of a plurality of trains of electrical impulses to information in the form of other trains of electrical impulses comprises, a plurality of apparatus groups, a lesser plurality of registers which are accessible to the said apparatus groups, and a trans- 'ice later which is available to any one of the registers, the arrangement being such that when, during operation, a plurality of trains of electrical impulses are supplied to any one of the said apparatus groups, that apparatus group, which is adapted to store the information of the first train of the plurality, obtains access to a register which stores at least the information represented by the plurality of impulse trains after the first, and the said translator subsequently effects the desired translator.

According to a feature of the present invention an arrangement for use at a switching centre of a telecommunications system of the kind in which trains of electrical impulses are employed to effect switch setting and which is adapted to translate information in the form of a plurality of trains of electrical impulses to information in the form of other trains of electrical impulses com} prises a plurality of apparatus groups, a lesser plurality of registers that are accessible to the said apparatus groups, and a single translator that is available over a plurality of routes both to any one of the said registers and to any one of the said apparatus groups so that when during operation the translator is so available to any particular register and to any particular apparatus group, the register is that one to which the apparatus group has access and the translation effected by the translator is determined by the information supplied by both the apparatus group and the register to which it is then available.

According to a second feature of the present invention an arrangement for use at a switching centre of a telecommunications system of the kind in which trains of electric impulses are employed to effect switch setting and which is adapted to translate information in the form of a plurality of trains of electrical impulses to information in the form of other trains of electrical impulses comprises a plurality of apparatus groups, each having a first group of terminals and a second group of terminals,

a lesser plurality of registers that are accessible to the apparatus groups, and a single translator available both to any one of the registers and to any one of the apparatus groups over a plurality of routes, the arrangement being such that when, during operation, trains of electrical impulses are supplied to the first group of terminals of any particular apparatus group, information relating to the said impulse trains is stored both by the the said register, and trains of electrical impulses representative of the translation being supplied by way of the said apparatus group to its second group of terminals.

One arrangement of part of an automatic telephone exchange in accordance with the invention will now be described, by way of example, with reference to the sixteen figures of the accompanying diagrammatic drawings in which:

Figure l is a schematic diagram of the arrangement,

Figures 2 to 4 are complementary illustrations of the electrical circuit of an apparatus group,

Figures 5 to 10 are complementary ilustrations of the electrical circuit of a register,

Figures 11 to 15 are complementary. illustrations of part of the electrical circuit of the translator, and

Figure 16 shows the manner in which Figures 2 to 15 should be arranged both to illustrate the electrical circuits of the individual units, that is the apparatus group, the register and part of the translator, and to illustrate the relationship between the electrical circuits of those units when employed in an arrangement according to the invention.

The arrangement comprises a plurality ofapparatus groups, a lesser plurality of registers and a single"transla-' 'tor and will be described in'its application to automatic telephone systems. In this application the said arrange- 'ment is employed;atafi'automatic telephone exchange to effect tr ansl'ationof the first three impulse trains of a series ofelefctrical'impulse trains when such a series is applied to anyoneof the said apparatus groups, there be ing 7 up to' ten impulses in .each train. ,The impulse trains of such aseries may be originated by means of a tele: phone that at a telephone'station that is connected to the said telephone exchange, each impulse train correspond'ing to a 'd'iifer'ent dialled digit, The first three impulse trains correspond to the so-called routing digits, r llereinafterreferredtoas the A B and digits, and

represent a-jiniqfiecode that is characteristic of the oh v jectivetelejihorte;exchange to which the wanted telephone I station is connected. The A, B and C digit impulse trains ar translated with or without change inthe num'. I

' bet of impulsesiir'i each train and with'orwithout change in;the numnerjer impulseftrains; The impulse trains resulting from"thegtranslation are employed to effect switch setting'soas to establish a signalling path over a a predetermined route, .whe'reafter the numerical digit im- "ings. n V r Let it .bejas'sum'ed that a, single prefix digit is' dialled by a calling party. The resulting impulse train is applied 'to a previously seized selector switch, as for example the two-co-ordinalte elect'ro-mag'ne'tic step-hy-s'tep switch at which is situated at the calling par'tys exchange This impulse train causes the wipers of the seized'switch to be teppedto a bank contact level, such; as the first that is'eharacteristic of the said 'piefiit digit. tacts of the said switch atthe first bank contact level are connectdto 'a'pp'arau's' groups and the switch stepsits wipers inftiiown manner around these bank contacts until affree apparatus group, such as the apparatus group 91, is ifund This apparatus group 91 is seized for use with thec'all.

Each 6f the said. apparatus groups: includes a step-bysfe'p 'uniselec'toi switch, hereinafter referred to as a register hunter switch, the bank contactsof which are associated with the-registers." The-seizedapparatus group 91 causes. its register. hunter switch 92 to'hunt for a f rec register su'c'has the register Q3 and to obtain access to that register. when found. Difficulty-may be experienced in completing both of the above switching-operations be fore the calling party-dials the said Adigit. In order o overcome this difiiculty the A digit impulse train, is

received on a further step-by step-'uniselector switch 94,

hereinafter referred to as the A'digit switch in the seized 1 apparatus group 91 The'saidA-digit switch 94 steps its a I p a V a t V g jwipersiaccording t :the p g rg of impulses iv the code selector that is connected by way of the line o ha th 'positio n of the switch wipers at the l g1 tmpnlseanaui digit. The said A digit switch 94 ha tact banksiand connections 95 are taken from succeeding uniselector switches TA and T] in the translator hfi. With 'a telephone system, it is usual for an impulse/train to comprise from one to ten impulses, so that up to ten} anagram j .1

Reference should now be 'niade to Figure of the. draw- The consuch connections may be provided, the, number employed being'dete rmined-by the circuit requirements: Preferably" no such. connection is taken from/the bank contact corre sponding to a single impulse forithesaid A digit, faulty;

5 operation of the A digit switch resulting from a spurious f In the arrangement impulse is then of no consequence.

under consideration nine .motor uniselector switches TA to TI are employed in the translator 99,: provision being thus madefor A lG' impulses.

The B and C digit im ulsetrains are Suirai e the? f seized register 93 by way'oftne registerhitiitei -switch '92 in the apparatus group 91 and are receigeduby the V register 93 on step-by-step nniselector switches," here 2 l5 inafter referred 'toafs'the B digit and C digit switches respectively, the wipers =of'each of these switches being 7 stepped accordingto the number of impulses in the re-' spective impulse trains;

digit i'mpulse trains of fromtrwo to ten" A 1step-'by-s tep unisel ector' switch 96, hereinafter rei V 0 fen-ed toas the allotter, is associated with the .translat'or f 1 99;: and has its bank contacts connected to the registers; When the seized register 93has .received'zthe Band C digit impulse trains it'applies a start signal to'the' allotter byway of the lead 97. It then the allotter is not already in use with anothercallrit: stepsfits .wipers to the bank 1 i contacts associated with the said register. "Potentials of predetermined polarity arethen applied to certaincona tactsof twoof the contact banks of the particular motor *uniselector switch, TA, say,.in the translaton'selected by j p 39 the Adigit switch. :T he contacts of the said contact banks f to which these potentials *are' applied are vicharacteristic of the B and Cdlg lt' impulse trains respectively, and it is V arranged that at only one position are the switch wipers associated with-the'said contact banks each in engagement with n bank contact'towhich thersaid potentialsare an marked by the said potentials whereupon signalsjarc applied over the bank contacts and associated wipers of theselected group at that position toa distribution frame '98. The resulting output signals from the distribution" frame 98are received and recorded by the'operationof' 5O electro-magnetic'relaysboth in the register 93' and in the apparatus groupfl, wherea'fter the translator 99 is released sofas to be available rm use with the setting up of another call. 7

Two alternative methods of operation will 'now' be p p considered at 'this stage. 'In the first method the signals received from' the translator 99 represent-the com-f p'lete translation. The said signalsare received by several groups of electromagnetic relays in the seized register 93 r and by a single group of electromagnetic relays in the seized apparatus group;91.- The relays operated in each group in the register '93 characterisera diiierent impulse train'of the route code and act to cause transmission of that impulse train in correct sequence'relative to the' other impulse train of the-'route'code to the-junction or 100 to theseized apparatus group 91. :Theielays 'of the. 7 group in the. apparatus group 91. thatrare operatedch ar- 1) charged th lland actto ucterisegthe-te a N g" cause the calling subscrrbers meter to fbe operatedac cordingly during thecall. a V (1 i In the 's'e'co d methodi to i-be hereinafter desijribed in;

more detail, ne grsu errelaysjis provided'ineach ire;

gister. and negron' in each apparatusgrohp. The

function-of thelatter groupis as describediabove, a I '7 relays operated in the former group of the seizedjregis I V plied. The remaining contact banksandassoci'ated wipers V of'the said motor uniselectonswitchTA maybe divided 'into two groups; the selected group being'determihed' by V ter 93 at this stage characterise the first impulse train of the route code and act to cause transmission of this train over the line 100. Subsequent to this transmission a suitable interval is allowed to enable the said first impulse train to effect its switching operation. After this interval, the register 93 and the apparatus group 91 again obtain access to the translator 99 in the manner previously described and the translator 99 supplies further signals to the said register 93 that are characteristic of the second impulse train of the route code. This process is repeated until all the impulse trains of the route code have been transmitted over the line 1% and the required signalling path has been established.

The impulse train corresponding to the numerical digit of the wanted partys telephone number are stored throughout the above operations on step-by-step uniselector switches in the register 93. After an interval in time sufiicient for the impulse trains of the route code to have extended the signalling path to the objective telephone exchange, the numerical impulse trains are transmitted over the said path whereafter the register 93 is released. The apparatus group 91 is held operated throughout the duration of the call.

When the distance between the exchange of the calling party and that of the wanted party is great, one or more further signal translating processes such as that described above may be necessary at intermediate points along the speech path. Provision may be made such that when a call is of this nature the original A, B and C digit impulse trains are re-transmitted after the route code and before the numerical digit impulse trains.

The arrangement described above will now be described in more detail with reference to Figures 2 to 16 of the accompanying drawings.

The apparatus group shown in Figures 2 to 4 comprises a register hunter switch having seven contact banks and associated wipers Rl-ll to Rl-I7, the A digit switch having six contact banks and associated wipers AD2 to AD6 and a plurality of electro-magnetic relays. The apparatus group may be seized for use with a call by looping the line wires 1 and 2. When this occurs the windings 88 and 89 of the relay A are energised in series from the negative battery at the winding 89 to earth at the winding 88 by way of the calling loop so that the relay A operates.

On the relay A operating the contacts A1 complete a circuit to operate the relay B and the contacts A2 prepare a circuit to apply earth to the lead 4 by Way of the wiper RHZ.

On the relay B operating the contacts B1 complete an alternative circuit between the negative battery 16 and the lead 11 ready for the subsequent stepping of the wiper AD1. The contacts B2 complete a circuit to energise the register hunter switch driving magnet RH. The contacts B3 prepare operating circuits for each of the relays DR, NU, MW, MX, MY and MZ. The contacts B4 prepare an impulsing circuit for the driving magnet AD of the A digit switch. The contacts B5 disconnect the wiper homing circuit of the driving magnet AD. The contacts B6 complete an energising circuit for the winding 90 of the relay CA. The contacts B7 prepare a holding circuit for the relay CO and the contacts B8 connect the operating windings 12 and 13 of the relay K which are in series with one another in series with the wiper RI-Ii.

On the relay CA operating the contacts CA1 further prepare the impulsing circuit for the driving magnet AD. The contacts CA2 prepare an alternative circuit to apply earth to the wiper RHZ so as to prevent signalling over this wiper during the subsequent impulsing of the relay A and the contacts CA3 prevent the relay NU from operating when the wiper ADS moves to its second bank contact. I

The register hunter driving magnet RH steps the wipers RH! to EH7 by self interruption of its energisiug circuit over the associated interrupter contacts 'Whe the Wiper RH reaches a contact of its associated bank that is connected to a free register the relay K operates in the manner hereinafter described. Let it be assumed that the register that is associated with the leads 3 to 9 and which is shown in Figures 5 to 10 to be free, that is not already in use with another apparatus group. This condition is indicated by the presence of negative voltage on the lead 3, so that when the wiper RH! steps to the bank contact to which the lead 3 is connected it completes a circuit to energise the windings 12 and 13 of the relay K in series.

On the relay K operating the contacts K1 complete a short circuit across the operating winding 12 of this relay so as to increase the current flowing through the other operating winding 13. The negative voltage on the lead 3 consequently falls since the battery from which this voltage is derived is connected to the lead 3 by way of resistance. Such an arrangement is hereinafter referred to as negative resistance battery, the battery 1% and resistor in in series being a typical example. The fall in voltage on the lead 3 prevents the seized register from being taken into use with another apparatus group. The contacts K2 open and remove the short circuit from the operating winding 15 of the relay KR which therefore operates. The resistance of this operating winding 15 is such that the driving magnet RH does not receive sufiicient current to operate further.

On the relay KR operating the contacts KR connect earth to the lead 4. The contacts KRZ extend the operating circuit of the relay KC to the lead 5. The contacts KRS extend the operating circuit of the relay CO to the lead 6. The contacts KR4 have no function at this stage and the contacts KRS and KR6 extend the leads 8 and 9 through to the outgoing line wires 16 and 7.

The leads 8 and 9 are connected together in the seized register so that a short circuit is applied across the line wires 16 and 17, that is the outgoing line from the seized apparatus group is looped. The line wires 16 and 17 may be connected to a junction, that is a circuit directly connecting the exchange of the apparatus group to another telephone exchange or alternatively to a selector switch whereby access is obtained to a junction. This selector switch, when provided, may be set by the first of the route code impulse trains. In either case it is arranged that the looping of the line wires 16 and 17 results in the application of positive and negative line potentials respectively to the said line Wires in a similar manner to that described above in connection with the seizure of the apparatus group.

On application of the A digit impulse train to the positive and negative line wires 1 and 2, the relay A responds accordingly by releasing for the duration of each impulse.

On each release of the relay A the contacts A1 open and break the operating circuit of the relay B. The relay B is of the slow to release kind so that it holds operated throughout irnpulsing. The contacts A2 complete an energising circuit for the driving magnet AD. The wipers ADI to AD6 are thus stepped around their respective contact banks one contact position for each impulse of A digit impulse train.

In moving off its first bank contact the wiper ADZ breaks the energising circuit of winding of the relay CA. This relay is however of the slow release kind so that it holds operated, its other winding 91 being energised in series with the driving magnet AD during impulsing. The wiper AD5 prepares a circuit to apply earth over the appropriate one of the leads 18 to 26, each of these leads being associated with a difierent motor uniselector switch in the translator.

The remaining wipers ADI and ADS to ADS have no function at this stage.

On the relay CA releasing the contacts CA1 break the energising circuit of the driving magnet AD. The contacts CA2 open an pr pare for subsequent impulsing to the seizedzregisterrover the leaclv 4.; "Ihe'contactsCA3 have noiunctiorr at thisstage;

. .The: A digit impulse. train has thus-been. received by.

the seized apparatus group which has in' the. meantime obtained access to the register shownin Figures to 10. Referring now to Figures 5 to IOQthe register there shown comprises a B digit switch having. five contact banks and associated wipersBDll to BDS, a C digit switch having. three contact :banks andassocifled wipers CD1 7 to CD3', four' uniselector'switches; wherebyhthe four numerical digits I of the wanted partys telephone numaber are stored during translation, the wipers of these switches being referenced M,j1C,lD-' and U respectively;

u 'two further. uniselector switches havlipg. wipers S1 to S5 and CNl. to CN6respectively and a plurality' of'electromagneticrelaysl 1 v r 7 When this register is taken intouse bythes'aid ap'-- paratus. group "the relay AR operates: the lead 4 being at earth potential.

On the relay AR operating the contacts ARI. complete a" circuit to operate relay BR and the contacts ARZ prepare an impulsing circuit for the B, digit switch driving magnetBD. a

;On the relay ER operating the contacts BRl prepare a circuit to operate the relayrCR. The contacts BR2 complete a circuit to hold the relay BR operated. The

' contacts 3R3, 3R4 and. BR6 have .no function'at this stage; The contacts BRS complete a circuit to operate the relay BA. Thecontacts BR. 7 prepare a circuit to energise the driving magnet CNQand the contacts BRS' disconnect the wiper homing circuit of each of the driv- 7 ing magnets BD; CD, M, C, D and U.

Ontherelay BA operating the contacts BA-l maintain the circuit for negative resistance battery. tothe lead 3 I ready for the wiper BD'S to move off its first bank contact;

' prepare "a circuit to operate the relay CR readyfor'the wires 1 and 2 of the apparatus group, the relay A releases for each impulse and the contacts A2 break the operating cireuit'of the relay AR in the register, The

" relay AR thus responds to each impulse of the B'digit impulse'train'by releasing momentarily. On each release of the relay AR' the. contacts ARI complete an'energising circuit for the winding 27 of the relay. CR and'the contacts ARZ complete an energising circuit for thc driving magnet BD.

the relay CR... This winding 27 is of high resistance so that after. the relay CR operateson the first release of' the relay AR, it holds. operated throughout the subsequent impulsing. The contacts ARZ break the energising circuit of'the'driving magnet BD so that the wipers BDl to EDS are stepped around their contact banks one con-- tact for each impulse in the B digit impulse train.

of the driving magnet U. Each of the switch wipers U1 to US is thus stepped to the second contact of respec? tive bank'.,' V 7 u The wipers 8131 to EDS have no function at this stage.

The wiper U4 prepares an energi'sing' circuit for the driving magnet'CD ready for the C digit impulse train. The wipers U! to US and US have no .functiomatthis 'stage. I e The relay AR responds to each impulse of the- C digit impulse train inthe manner described above. 'Th'e wipers CD1 to- CD3 "of the digit switch are thus stepped around'theircontact banks'one contact for each impulse at this stage. a

ofi'the train, The relay'CRbperates at the contmencement "ofvinipulsing its contacts CR1" completing antene'rgising circuit forhthe driving magnets U. Qn th'e relay 313R releasing atTthe-end of-impulsing. the' driving 5 a magnet- Urelea'se's; and each of the switch. wipers U1: t'o

7 lead 2% The contacts RS3 connect ear'thatof the. lead: a 7

'29 and thecontaets RS4,RS5 and. RS6 have no function Each of the impulse trains. corresponding to. the nu-j merical digits of. the wanted subscribers telephdnenum-- V .7 her. are received by'the'register in themanner previously" described in connection with the B.and..C digit impulse .ytrainsa' ilarly the second and third numerical digitrtr'ains step" the switch Wipers C1: to C3 and the wipersD l. to D3 respectively while each of thewipers U1 to USis stepped to the fifth and then the sixth contact of, its associated? bank. The impulses of th'eplast numerical digitjttrain 39 steps each of the wipers UI to US around its associated contact bank starting from thesirr-th bank contact in teach case. H As previously described; negative resistance;- battery and earth are applied to the leads 28and- 2% at the termi-.

-nation of C digit impulse train; Theseieads '28 and 2 together with thelead- 39 are conne'ctedtothallotter switch shown in-Figure l4;and* reference should now. be 7 rnadetothistigure. i 1. i

The relay ST operates to ea rth on the lead 29 i u I On the relay SToperating the contacts ST1 prepare an" operating circuit for the relay AK and-the contacts 8T2; e complete an:energ isin g circuit for the allotter. switch driving magnet AL by'way o'f'theassociatedinterrupter j contacts ALdr/g. The wipersi Al lil andALZ arethere I 0 tom stepped by self interruption of the driving magnet} wiper ALZ reaching this contact the [relay AK operates from the negative potential on the lead .28. On the relay H V AK operating the contacts AKI break the energising On each intervening operation 'of the relayAR the contacts AR} apply a short circuit to the winding 27 of circuit of the driving-magnet-AL andisoprevent further stepping of the switch wipersALl and AL2. The con-- 'tacts AKl also complete a circuitrto operate the relay 'On the relay 'AH operating, the contacts AH'l'further disconnect the. energising circuit of thedriving magnet. AL; The contacts-AHZ connect earth to thelead 39- so that the relay, KA in the'register operates, and the contacts AH3' prepare. a circuit to, hold'the relay op erated;

In the register (Figures; 5 to 10):. On theTrelay KA operating the contacts KA l complete a circuit to operate 7 the relay KB. The contacts KAZ connectearth to the" .lead 5 and so. complete :a circuitv .to. operate the relay 'KC in the apparatus group. The contacts KAT connect;

earth to the lead '31 which 'is connected, together with the'leads 32, 33 and 34; tothe translator. The contacts KA4 to KAS have no function atthis stage,

On the relay: KB operating the contacts K131 connect earth to the switch wiperBDf and-thence by way of one 7 battery to the appropriate one of the leads 37 to 4L 

